Questions: Which of the following is true about vitamin D synthesis? a. Smog or heavy cloud cover does not block the sun's ultraviolet rays that promote vitamin D synthesis in the stain. b. Tanning lamps do not stimulate vitamin D synthesis. c. Sunscreens with an SPF of 10 or above prevent the synthesis of vitamin D. d. Dark-skinned people require more sunlight exposure than light-skinned people to make an equivalent amount of vitamin D.

Which of the following is true about vitamin D synthesis?
a. Smog or heavy cloud cover does not block the sun's ultraviolet rays that promote vitamin D synthesis in the stain.
b. Tanning lamps do not stimulate vitamin D synthesis.
c. Sunscreens with an SPF of 10 or above prevent the synthesis of vitamin D.
d. Dark-skinned people require more sunlight exposure than light-skinned people to make an equivalent amount of vitamin D.

Transcript text: Which of the following is true about vitamin D synthesis? a. Smog or heavy cloud cover does not block the sun's ultraviolet rays that promote vitamin $D$ synthesis in the stain. b. Tanning lamps do not stimulate vitamin $D$ synthesis. c. Sunscreens with an SPF of 10 or above prevent the synthesis of vitamin $D$. d. Dark-skinned people require more sunlight exposure than light-skinned people to make an equivalent amount of vitamin $D$.

Solution

The answer is the fourth one (d): Dark-skinned people require more sunlight exposure than light-skinned people to make an equivalent amount of vitamin D.

Explanation for each option:

a. Smog or heavy cloud cover does not block the sun's ultraviolet rays that promote vitamin D synthesis in the skin.

This statement is incorrect. Smog and heavy cloud cover can indeed block or reduce the amount of ultraviolet (UV) rays reaching the skin, thereby reducing vitamin D synthesis.

b. Tanning lamps do not stimulate vitamin D synthesis.

This statement is incorrect. Tanning lamps emit UV radiation, which can stimulate vitamin D synthesis in the skin, although the safety and health implications of using tanning lamps for this purpose are controversial.

c. Sunscreens with an SPF of 10 or above prevent the synthesis of vitamin D.

This statement is partially correct but misleading. Sunscreens with an SPF of 10 or above can significantly reduce the skin's production of vitamin D by blocking UVB rays, but they do not completely prevent it. Some UVB rays may still penetrate and allow for some vitamin D synthesis.

d. Dark-skinned people require more sunlight exposure than light-skinned people to make an equivalent amount of vitamin D.

This statement is correct. Melanin, the pigment in the skin, reduces the skin's ability to produce vitamin D from sunlight. Therefore, individuals with darker skin require more sun exposure to produce the same amount of vitamin D as those with lighter skin.

In summary, option d is the correct statement regarding vitamin D synthesis.

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